Centrifugal or cyclonic type separators, also commonly referred to as cyclones, are very well known in the prior art. As it also well known, this type of separators for solid and gaseous materials operate with practically the same efficiency under pressure and under suction. They commonly comprise an upper cylindrical body which is continued downwardly by a lower or dust collecting frustoconical body, said upper cylindrical body having a tangencial inlet for the mixture of gas or solid material to be separated and a vertical duct to serve as the outlet of gases, whereas the frustoconical lower body has a lower opening to serve as the outlet for the separated solid materials.
In induction or suction type cyclonic separators, it has been generally preferred to provide the upper body also with a frustoconical shape, with the larger diameter opening directed downwardly and with a lower body of larger conicity directly joined thereto to form a continuous surface with said upper conical body. The inlet for the mixture of gas and solid material is also arranged tangentially on the wall of said slightly conical downwardly diverging upper frustoconical body, and the outlet duct for gases which is under suction in this particular instance, is arranged vertically on the upper lid of the upper frustoconical body.
The cyclonic type separators known in the prior art, of course, are reasonably efficient to separate various sizes of solid particles entrained in a gas, but show serious drawbacks when the materials to be separated are of the fatty type or of any other characteristics that may render the particles adherent, inasmuch as, even when said particles do not tend to stick to the inner downwardly diverging conical surface provided in the upper bodies of the induction type cyclones, they do tend to be trapped in the corners formed at the joint of the upper frustoconical body and the lower frustoconical body, and they also tend to be adhered over the whole surface of the lower frustoconical body, inasmuch as the latter is downwardly converging and presents an interior surface subject to the action of gravity on the particles falling thereon.
Obviously, the above represents a serious drawback, because it generally requires a cleansing operation and, in extreme cases, it may cause obstruction in the equipment or at least defective operation thereof, wherein the separation of particles is not carried out correctly.
Therefore, for long it has been sought to device a cyclonic separator which, without loosing the efficiency for separating particles of different densities or specific gravities entrained in a gas stream, would be sufficiently efficient to maintain all the inner surfaces of the apparatus absolutely clean, regardless of the fact that sticky or adherent materials are being handled which tend to build up at the corners and over the surfaces subject to the action of gravity in the interior of the equipment.